Ketonization of valeric acids over ZrO2-based catalysts synthesized by the sol-gel method

Details

Supervisors

Debecker, Damien P.

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en chimie et bioindustries, à finalité spécialisée

Abstract

Conventional production methods have had a significant environmental impact, particularly due to CO2 emissions and reliance on fossil fuels. With growing energy demand and increasing concerns over greenhouse gas emissions, there is a rising interest in sustainable alternatives. Lignocellulosic biomass valorization, which is an abundant feedstock, presents a promising solution for sustainable energy, chemicals, and materials production. Especially biobased carboxylic acids are interesting compounds that can be obtained via 2 different treatments of lignocellulosic biomass: fast pyrolysis and acid hydrolysis. Further these compounds needs to be upgraded, which can be done by catalytic ketonization. This upgrading reaction presents many advantages as oxygen content removal (increases the calorific energy), acidity reducing (easier processing) and chain elongating (added value and easier extraction). Majority of studies have extensively investigated ketonization of shorter carboxylic acids (C2-C4), but there is limited research on longer chain carboxylic acids. It is in this context that my master thesis aims to develop heterogeneous catalysts active for C5 valeric acid ketonization into 5-nonanone. Previous work have demonstrated the effectiveness of amphoteric and high lattice energy metal oxides, particularly ZrO2, for this reaction. Therefore, this work aims to explore the incorporation of ZrO2 with other metal oxides possessing advantageous properties to seek for emerging activity and properties. To this end, mixed oxides of CeO2/ZrO2 with varying loadings (10, 25, 50, 75, and 90%) have been synthesized using the sol-gel method and been studied in gas phase ketonization at 350, 400 and 450°C. The results indicates that CeO2/ZrO2 mixed oxides, specifically at low loadings (10 and 25%), demonstrated a synergistic effect compared to their respective single oxides. Moreover, 10 wt.% CeO2/ZrO2 showed outstanding stable activity for +35h. The reason behind this phenomenon is the stabilizing effect of CeO2 on t-ZrO2, which preserves its crystallinity from alteration during the reaction. Conversely, ZrO2 has demonstrated quick deactivation due to its thermosensitive crystal phase that undergoes a transition from t-ZrO2 to m-ZrO2. Furthermore, it has been shown that this transition is linked to sintering, resulting in larger crystallite size and altered textural properties. All in all this master thesis highlighted the significant role of specific crystal phase (e.g. t-ZrO2) in determining VA ketonization catalytic activity on mixed metal oxides.